Hi !
So I see this construct:
if (test_and_set_bit(0, &chip->opened))
return -EBUSY;
.../...
return 0;
_error:
dprintk(1,"Error opening PCM!\n");
clear_bit(0, &chip->opened);
smp_mb__after_clear_bit();
return err;
So that's basically an attempt at doing a spinlock. The problem is your
barrier is wrong at the end. Better would be:
done:
smp_mb__before_clear_bit();
clear_bit(0, &chip->opened);
Though it's still less optimal that doing:
if (!spin_trylock(...))
goto bail;
.../...
done:
spin_unlock(...)
If you really want to stick to bitops, then you may want to look at
Nick's upcoming patches adding some bitops with appropriate lock
semantics.
Cheers,
Ben.
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